Stepped area chart not considering dates properly.

Are your dates text strings or real dates? What kind of chart are you using? Assuming your dates are real dates and not text strings, it should be as simple as choosing a chart type that supports a numeric x axis (like a scatter chart) or a date x axis (like a line chart). If your dates are text strings, then you would want to convert them to real dates and then use a chart with a numeric or date axis.

This is a bit old, but has a good description of the different axis types in Excel: https://peltiertech.com/Excel/Charts...ValueAxis.html

Have you seen this group of methods? https://peltiertech.com/step-charts-in-excel/ The one method using error bars does not require duplicating the data. it does require using a scatter chart rather than a line chart and it will require computing delta-x and delta-y values somewhere in the spreadsheet. Are you similarly constrained in that you cannot have any ancillary data anywhere in the spreadsheet, or would you be allowed to add some detla-x and delta-y columns somewhere?